The present invention relates to configurable input devices for industrial automation and motion control equipment, and in particular operator panels for use in industrial environments. Operator panels are used as man-to-machine interfaces that are found typically with industrial automation equipment to control machine functions.
Industrial operator panels that are small and low-cost currently are available commercially in fixed button configurations, which use membrane foil buttons or short-stroke push keys. Both of the fixed button input technologies use applied force to buckle or elastically deform a component in order to produce an electrical connection between electrodes. These technologies are inexpensive, robust, resilient to harsh environments, and provide tactile and audio feedback to the user. These membrane buttons typically are low voltage on/off switches, and the push keys are typically used as plug-and-play switches.
For industrial operator panel use, the membrane buttons and individual short-stroke push keys are relatively inexpensive compared to other more sophisticated types of input devices for operator panels, but they have significant drawbacks. For example, membrane buttons can cost approximately $7 per sheet of 60 membrane buttons and push keys can cost about $2 per push key. For a typical operator panel, the short-stroke push keys are more expensive than membrane buttons. As the number of required keys increases for more sophisticated operator control panels, the cost can become unreasonable with short-stroke push keys. Membrane buttons, on the other hand, have other drawbacks. For instance, after repeated use, membrane buttons wear easily such that the convex foil loses its ability to spring back after repeated buckling, rendering the button useless. Also, membrane buttons do not always work well in low-pressure environments (e.g., buttons may stay depressed inadvertently).
These types of technologies, however, have a major limitation in that operator panels utilizing these technologies cannot be customized easily by end users who may have a need to change frequently the features and capabilities of the operator panel. That is, there is currently no easy method to add/remove buttons, change the button locations, change the button sizes or shapes, change the force required for button activation, or add custom graphics. At present, end users that desire customized operator panels have two solutions. The first solution requires the end user to redesign and retool machines that produce the panels discussed above. Typical retooling costs for the membrane button sheets are currently about $25,000 or more. Compared to the cost and effort to retool, the easier and less expensive second solution is using touch screens.
For applications that require unique button configurations or button configurations that need to change periodically, expensive touch screens are currently the only commercially available option. Unfortunately, touch screens provide flexibility only at a high cost with their lack of durability and robustness. Industrial touch screens are fully graphic, touch sensitive LCD displays that facilitate operator control and process monitoring on the same screen. Touch screens do not use physical keys, but rather virtual buttons that are displayed on the screen. The touch screen senses pressures at the locations of the virtual button. Since buttons and controls are created in software, the location, shape, and function of the virtual buttons can be programmed to change as often as necessary. The configuration of the virtual buttons is stored usually on a computer (PC or PLC) that is inside the touch screen housing or connects to the touch screen via cabling. The computer must include the electronics and particular video drivers to display properly the virtual buttons on the LCD. Touch screens are, however, delicate when compared to other input devices and may have difficulty withstanding the harsh treatment or environments found in industrial automation. For example, touch screens do not absorb well any strong impacts or concentrated loads and touching a virtual button with, for example, a screwdriver tip can damage seriously the sensor or scratch significantly the outer surface of the touch screen. Touch screens also may not be able to withstand inputs exceeding a certain level of pressure. The corrosiveness of some environments may not allow the computer and its touch screen to endure for the long periods of time needed to justify their initial expense and costs of their eventual replacement.
Touch screens are expensive when compared to off-the-shelf membrane buttons or push-keys. If an operator panel placed in a harsh environment needs to be reconfigured frequently, a touch screen would be the only option despite its physical vulnerabilities.
Other configurable input devices without vulnerable displays exist currently, but they are not used in industrial automation and are intended for home or office computer input. Two examples of typical input devices include programmable keyboards and digitizing tablets.
Programmable keyboards typically are standard push key computer keyboards that may include extra push keys. The design of the push keys is similar to (but considerably less durable than) the short-stroke push keys found on industrial operator panels. In general, these keyboards have the ability to program a plurality of keys to respond with a series of standard ACSII symbols. The key information may be stored in non-volatile memory in the keyboard or in computer memory. Limitations in sealing and durability are the main deterrents to using these types of keyboards in an industrial setting. Additionally, these keyboards have the same problems as industrial short-stroke push key panels and membrane button panels: the keys are fixed in position, cannot change size, have a predetermined, constant activation force, and cannot easily accept custom graphics.
Some digitizing tablets allow users to define areas of the tablet as virtual buttons when used with specific computer aided design (CAD) software. For example, CadPRO by GTCO CalComp, Inc. ships with software that can be used with AutoCAD 2000® (AutoDesk, Inc). Virtual button information is configured and stored on a personal computer. Several devices provide a sleeve for the user to place a printed copy of the virtual button layout. When the user places a special pointing device on an area of the digitizing tablet that corresponds to a virtual button and presses a particular button (or the pointing device or computer keyboard), the CAD software is instructed to perform the virtual button function. All of the digitizing tablets require a personal computer to operate, need to be used with a special pointing devices such as special optical pens etc., and are not designed to be used in caustic environments. Additionally, these CAD digitizing tablets can be expensive and are typically used for engineering design applications in offices, rather than in industrial settings that have harsh environmental conditions.
Accordingly, there is a need for an alternative type of operator panel that is configurable, durable, and inexpensive operator panel and capable of being used in sophisticated industrial automation and motion control environments. As seen from the above, the current choices are between low-cost, non-customizable industrial operator panels and expensive, high-end touch screens.